Typically, mattresses found in the marketplace include a series of coiled springs that are supported by cross members to keep the spring ends from bucking off axis or moving horizontally, and to achieve a certain amount of flatness. Cross members typically have small coils that are looped through the ends of the main coiled springs. If the ends are not supported by the cross members, the diameter of the spring must be large enough to resist instability (moving horizontally) or bucking.
A main problem with existing mattresses is that when the spring quantities are increased, cross members are added due to the instability of the spring ends. The cross members effectively reduce the independency of the springs. A load on one spring location will transmit that load to adjacent spring locations due the cross members. Also, the load rate as the spring is being compressed increases exponentially. Due to this effect, the body will experience pressure points and nonconformance to the body.
In existing mattresses that contain no cross members, the spring diameter will generally be large to prevent the spring from buckling off axis, and as a result the number of springs in the mattress must be reduced for space reasons. Consequently, the spring rate of the springs will be increased to compensate for the reduced number of springs in the mattress, and the body will experience pressure points and nonconformance to the body.
Another problem with existing mattresses is that the spring coils are exposed so that the mattress requires more insulation between the spring coils and the body.
Other prior art mattress designs include solid layers of latex foam (no spring design) and/or viscoelastic (memory) foam in combination with other foam. A main problem with these designs is related to the horizontal tension strength and shear strength of the material. The adjacent foam is affected by the nearby load from the body and does not act independently, and this gives rise to pressure points. Another problem with such designs is that the spring rate is generally constant throughout the mattress surface. Therefore, the spring rate can not be varied in different sections of a mattress. Another problem associated with viscoelastic (memory) foam is that it is slow to respond to body movement, as a person turns or moves in bed, and this can limit or make movement more difficult once the foam forms a set.